What is a Closed Cooling Water System?
A closed cooling water system is one in which there is no make-up after the initial charge (except to replace accidental leakage) and no blowdown. Because this arrangement gives no opportunity for evaporation, the water chemistry, once established, can be easily and inexpensively maintained. These systems are used primarily when precise control of temperature or water purity is necessary. They are found in automobile radiators, tempered water systems, and in some pharmaceutical manufacturing processes. The heating of the cooling water that occurs in a closed system is removed by an air-cooled heat exchanger or other external cooling system.
In contrast, an open cooling water system is one in which some amount of make-up water is required on a continuing basis. Cooling water systems with a cooling tower are an example of open cooling water systems. (See Figure 1.)
Closed Cooling Water Systems… How Corrosive are They?
Because of the design features described in the preceding paragraphs, closed cooling water systems should have essentially no corrosion or fouling. The cooling water is relatively easy to control, at least in theory. There should also be essentially no water loss from the loop and no make-up required.
However, there are several factors to consider to ensure that the system is truly closed and that little or no make-up water is required.
